1. Field of the Invention
The present invention relates to a casting method and a casting mold for casting a product having a body, an opening provided so as to pass through that body, an island arranged inside the hollow away from the body, and a connecting portion connecting the island and the body, in particular a case of casting a product with thicknesses of the body, island, and connecting portion of 1.5 to 4 mm. Note that here, the term “mold” is used in a sense including both “molds” and “dies”.
Further, the present invention relates to a die casting mold of a three-part mold structure using three molds to form a thin die casting or a complicatedly shaped die casting.
2. Description of the Related Art
In the past, for example in the die casting method for casting a product used for various parts, a cavity having the same shape as the product has been formed between a pair of molds and a melt of metal has been filled in the cavity to cast the product.
In this die casting method, a gate serving as an inlet for the melt in the cavity and a runner for guiding the melt poured from a pouring portion into the gate are provided between the pair of molds. Further, the melt is poured into a sleeve at the pouring portion and the melt injected to the runner by a plunger to fill the melt in the cavity from the runner through the gate.
With this conventional casting method, it was difficult to produce a casting having a complicated shape or a thin casting. For example, it was difficult to cast a part having an opening provided so as to pass through the body and having inside that opening an island arranged separated from the body and a connection portion joining the island and body.
That is, in a casting having such an island and connecting portion, the melt flowing from the runner to the body has to flow to the island through the connecting portion. It is however not easy to feed melt from the body to the connecting portion and island. In many cases, the melt is not sufficiently filled there—resulting in casting defects.
The problem of casting defects can be said to occur not only in the die casting method, but also general casting methods. Therefore, a casting method able to produce a casting having an island and connecting portion easily and with a high quality has been desired.
In another respect, almost all die casting molds for forming the die castings are of two-part mold structures having a fixed mold having a connection sleeve for injection of the melt and a movable mold able to move relative to the fixed mold and forming a die casting in a cavity formed between the fixed mold and movable mold. As opposed to this, the inventors discovered a three-part mold structure die casting mold provided with an intermediate mold between the fixed mold and movable mold.
In this three-part mold structure die casting mold, the melt injected from the connection sleeve is filled into a cavity formed between the intermediate mold and movable mold through a runner formed between the fixed mold and movable mold and a pin gate formed at the intermediate mold. Afterwards, the intermediate mold is moved with respect to the fixed mold, then the movable mold is moved with respect to the intermediate mold and the die casting formed in the cavity is taken out.
Note that as prior art documents related to the invention of this application, there are Japanese Unexamined Patent Publication (Kokai) No. 58-199131 and Japanese Unexamined Patent Publication (Kokai) No. 3-136822.
This three-part mold structure die casting mold can form a thin die casting with a thickness of for example 1.5 to 4 mm or a die casting with a complicated shape while prevent casting defects. Therefore it is not suitable for forming a thick die casting with a thickness of for example over 4 mm or a die casing with not that complicated a shape. Further, in this case, use of a conventional two-part mold structure die casting mold facilitates handling and facilitates maintenance etc. since it is simple in structure.
That is, the above two-part mold structure die casting mold and three-part mold structure die casting mold each has its advantages and disadvantages. Therefore, a die casting mold having the advantages of both has been desired.